1. Field of the Invention
This invention relates to means for detection of localized over-heating of electrical power transformers and, in particular, to a telemetric system for such detection.
2. Brief Statement of the Prior Art
Electrical power transformers are commonly supplied with temperature indicators that reflect the average electrical loading of the transformer. Commonly, the transformer windings are sealed within a case that is filled with a heat-conductive liquid such as oil and the like. The electrical loading of the transformer is commonly measured by a replica device such as a coil that receives electrical energy in proportion to the total loading of the transformer. Temperature transducers are located in the replica coil and are coupled to indicators external of the transformer case for indicating the temperature of the replica coil, thereby indicating the average temperature condition of the transformer windings. Additionally, temperature indicators are located at various positions in the liquid within the transformer case.
A common difficulty of the aforementioned temperature instruments is that these instruments only determine average loading of the transformers and are not capable of detecting localized over-heating or hot spots such as occur by shorting between adjacent turns of the windings. The latter malfunction develops electrical eddy currents, resulting in inefficient transformer operations and severe overheating that leads to destruction of insulation and ultimate failure, particularly during peak loading conditions on the transformer.